ALERT: Data Show Increased Whooping Cough Prevalence in California

What’s Happening

HQI, through its Sentinel Signal Detection System, has identified an increase in pertussis (whooping cough) prevalence at California hospitals since the start of the second quarter of 2023.

Specifically, of the 88 California hospitals that provided 2023 Q2 hospital encounter data to HQI, 20 (22.7%) had higher than expected prevalence of pertussis cases among their emergency department encounters, inpatient admissions, or both. The number of cases at these hospitals was significantly higher than their median number of cases for the past five quarters. The hospitals experiencing increased pertussis prevalence are throughout California but particularly in the Inland Empire. It is important to note that hospital case rates are likely an underestimation of the prevalence of whooping cough in the population as asymptomatic or subclinical cases may not lead to hospital encounters.

The elevated prevalence of whooping cough is not limited to California. According to the Centers for Disease Control and Prevention, the U.S. is facing a notable rise in whooping cough cases and has seen spikes every three to five years. Consistent with this pattern, California last experienced a large increase in cases in 2019 Q2. 

What to know

Hospitals must be vigilant about whooping cough, especially as flu season, spikes in COVID-19 cases, and the spread of respiratory syncytial virus converge this winter. Hospitals are vital in providing prompt treatment with antibiotics, patient education on vaccinating pregnant mothers and young children, and maintaining a fully vaccinated workforce.

For more information

These alerts are made possible by timely hospital submissions of hospital encounter data to the Hospital Quality Improvement Platform and safety reports to the Collaborative Healthcare Patient Safety Organization. Thank you for helping us provide timely, accurate alerts to you and other members. Your data powers our Sentinel Signal Detection System and allow us to generate actionable alerts and assist in improving patient safety.

Questions or comments about this alert should be directed to HQI’s Kamali Jones ( or Vivian Eusebio (


[1]CDC, “Pertussis (Whooping Cough),” 8 August 2022. [Online]. Available: [Accessed 31 October 2023].